Alloy



Patented Oct. 26, I937 rarest car es Amer Anthony G. deGolyer, New York, N. it.

No Drawing. Application August 22, 936, Serial No. 97,422

2 Claims.

The present invention relates to a new and useful alloy'and relates particularly to an alloy containing boron, chromium, vanadium and cbalt, which is characterized by being responsive to thermal treatment for the improvement of physical properties.-

An object of the present invention is to provide an alloy especially adapted for use as metal cutting tools, the cutting eiflciency of which is superior to that of present known high speed steels and other alloys. A further object is to provide an alloy which is free from, or substantially free from carbon and which is readily amenable to thermal treatment, by means of which the hardness, tensile strength, cutting efilciency and other physical properties and characteristics may be accurately controlled over a comparatively wide range.

I have found through experiment that by alloying or otherwise intimately combining boron, chromium, vanadium and. cobalt within the range of boron 0.50% to 3%, chromium 8% to 30%, vanadium 1.50% to 8%, and cobalt substantially the balance, that I obtain metallic compositions which possess in combination materially improved physical properties compared to those of heretofore known alloys or compositions intended for the cutting or working of metals.

30 Alloys of this invention may be used in'the cast condition but approximate maximum values of hardness, resistance to impactand certain other important physical properties can be developed only through thermal treatment, or through mechanical working and subsequent thermal treatment. Bodies of the alloys which.

have been subjected to such treatment are particularly valuable for use as tools, dies and the like for the cutting or mechanical working of metals.

Numerous metallic compositions have heretofore been proposed as improvement on the generally known 18-41 type of tungstenchromium-vanadium high speed tool steel, and while many of such compositions possess greater hardness than such steel, all of them have disadvantages which render them unsuitable for general application as metal cutting or forming tools. Sintered or semi-fused compositions containing principally carbides of tungsten, molybdenum or tantalum bonded with a relatively soft matrix metal have a high degree of hardness, but are extremelybrittle. Cast compositions of the types heretofore proposed require the pres- 55 ence of at least 1.50% carbon to qualify as metal cutting tools and, as is well known, such alloys are not only brittle, but are so sensitive to varw disadvantages of the heretofore proposed com-.

positions is that none of them are responsive to thermal treatment for regulation of physical properties, and consequently physical properties and characteristics are governed entirely, by the chemical composition of the sintered or cast material.

My alloymay be used in the as-castcondition, or it may be-forged and rolled or otherwise mechanically-worked. I have found that both the cast and forged material are amenable to thermal treatment. For example, cast bodies of this alloy may have a hardness of from to 60 on the Rockwell C.scale and by subjecting the material to suitable thermal treatment, such -as quenching from a temperature higher than approximately 1000 C., the' hardness may be lowered to an approximate range of from 40 to- 47 Rockwell C. In this condition the bodies may be ground, shaped or formed, as desired. The alloy may subsequently be submitted to a second thermal treatment, such as heating to a temperature of less'than 1000" C. for a period of one hour or more, by which the hardness may be increased to from approximately 60 to '70 Rockwell C. In the latter condition the alloy is especially valuable forthe cutting or mechanical working of a large number of metals and alloys, as well as numerous none-metallic materials. An important property of the alloy is that virtually all of the maximum hardness, developed by thermal treatment, is retained when the alloy is subjected to elevated temperatures, e. g. such as are generated in the tip of a tool cutting metal at high speed. Although the alloy has a high degree or hardness and resistance to abrasion by hot metal chips, especially after thermal treatment, it is remarkably resistant to failure from sudden or repeated shock. Therefore, tools made of the present alloy retain an efllcient cutting edge for longer periods than other tools.

The more important .distinctive and valuable advantages are, apparently, due to the presence of appreciable amounts of boron in the composition, in conjunction with the other essential component elements within the percentages specified herein.

Specific examples of compositions within the scope of the present invention which I have found well adapted for metal cutting tools, dies and the like are the following: boron 1.20%, chromium 2 13%, vanadium 6%, cobalt balancej boron 2.10%, chromium 20%, vanadium 4%, cobalt balance.

An objective of the present invention is to provide alloys having high hardness, advantageous metal cutting properties, etc., which are free or substantially free from. carbon, and thus,

eliminate all of the serious disadvantages associated with carbon containing non-ferrous alloys or compositions intended for metal cutting tools. AlthoughAI prefer to have the alloys of this invention entirely free from carbon, in many inv stances I have found it'present in the nature of" an impurity incidental to manufacture. It is important 'to restrict the amount of carbon so present to a maximum of about 0.15%, as I have found that the presence of higher percentages of this element make the alloy brittle and impossible to forge, and also inhibits the desired and necessary reactions during ment. Furthermore, the presence of appreciable amounts of carbon decreases the red hardness of the alloy, i. e. hardness at temperatures of approximately 550 C. and higher.

By reason of the fact that the elements forming the essential components of the alloy of the present invention invariably are contaminatedwith other elements when produced in commercial quantities, the alloys of my invention usuallycontain insignificant amounts of one or more elements in the nature of impurities incidental to manufacture. The amount of such impurities should be restricted to percentages which are not effective onthe physical properties or characteristics of the alloy, nor on the physical reactions during thermal treatment. I have found that theamount of anypne of silch incidental impurities should not exceed a maximum of 1%. The presence of larger amounts of such'impurities, particularly silicon and aluminum, materially decreases the resistance of the alloy to failure under shock and impact during cutting operations, and,

further, inhibits the desired physical reactions during thermal. treatment. Therefore, the-presence of effective amounts'of impurities, such as carbon, silicon and aluminum, act to appreciably thermal treatlower the cutting efilciency and general value of the present alloy. l

My investigations indicate that the preferred structure of a body of the present alloy, particularly after thermal treatment, comprises at least two principal constituents: one, a relatively hard intermetallic compound of boron with one or more of the other essential components; and second, a solid solution of two or more of the essential components which has a lower degree of hardness and functions as a matrix. In some instances the structure will contain a third con posed of heretofore known alloys or metallic com- P sitions.

By the term "the balance substantially cobalt" in the foregoing and in the following claims, I intend that the alloy of the present invention comprises boron, chromium and vanadium within the percentage limits specified, with the remainder cobalt except for ineffective amounts of impurities which may be present. incidental to manufacture.

I claim: r

1. An age hardened alloy containing boron 0.50% to 3%, chromium 8% to vanadium 1.50% to 8%, the balance substantially cobalt.

2. An age hardened alloy characterized by being responsive to thermal treatment for eflecting precipitation hardening comprising boron 0.50% to 3%, chromium 8% to 30%, vanadium 1.50% to 8%, the balance substantially cobalt.

ANTHONY G. DE GOLYER. 

